The prior art provides various types of multiple position rotary switches for use in connection with electrical devices.
One example of a prior art multiple position rotary switch may be found in Erickson, et al., U.S. Pat. No. 4,131,771. The Erickson, et al. switch comprises a wheel attached to the end of a shaft. The wheel is mounted within a housing between a pair of circuit boards. A spring loaded detent engages serrations provided along the outer diameter of the wheel in order to retain the wheel in preselected positions. The top and bottom of the wheel each include a plurality of brushes that contact the circuits formed on the circuit boards as the shaft rotates the wheel. The circuit boards are permanently held in position by meltable pins. More particularly, after the circuit boards are properly aligned with the wheel sandwiched therebetween, the pins are melted in order to permanently secure the boards in position. Thus, as a result of this permanent form of mounting, the replacement or substitution of the circuit boards with other circuit boards having alternate circuit configurations is not readily possible.
Another example of a prior art switch may be found in the Model 77 Multimeter produced by John Fluke Mfg., Co., Inc. of Everett, Washington. The switch utilized in this device comprises a circular non-conductive stationary disk having mounted on each of its major surfaces a plurality of posts. A smaller rotatable disk is provided in the center of the stationary disk. Each side of the rotatable disk includes a pair of contacts which serve to complete connections between the posts located on each side of the stationary disk as the rotational disk is rotated. The posts are electrically connected to the main circuit board of the device and are permanently held in position upon the stationary disk by rivets.
The prior art further provides an electrical device distributed by the assignee of the present invention. The electrical device includes a switch mechanism having a race that is integrally formed into the top cover of the electrical device. The top cover includes an opening through which a portion of the knob of the switch mechanism extends. The race extends around the entire diameter of the opening along the inside surface of the top cover. The knob is retained within the opening by a circuit board that is mounted to the top cover such that a portion of the knob is sandwiched between the circuit board and the race. The circuit board includes both the circuits which serve to electrically interconnect the electrical components mounted upon the board and the switching circuit which provides the switching functions for the device. The race includes a plurality of spaced arcuate protrusions that form multiple peaks and valleys along the race. The knob comprises a cylindrical disk having on one surface a handle and at the opposite surface a protruding rim. The rim includes a first and second pair of diametrically opposed upstanding platforms. The first platforms are of sufficient size that rotation of the knob, the first pair of platforms glide along the peaks of the protrusions. The second platforms each include a socket for receiving a spring and a ball bearing. The bearing is located on top of the spring such that the ball bearing is sandwiched between the spring and the race. The spring provides a biasing force which retains the bearing against the rate such that as the knob is rotated, the bearing aligns itself in the valleys of the race thereby mechanically stabilizing the knob in preselected positions. Between the preselected positions, the bearing is received within the socket so as to allow the bearing to slide over the top or peaks of the protrusions. The knob includes along its opposite end a plurality of wiping members that rotate with the knob and contact the switching circuit thereby selectively closing the switching circuit as the knob is rotated to preselected positions. In this electrical device, the wave soldering of the electrical components upon the circuit board is not feasible because of the possibility of the switching circuit being damaged during the wave soldering process.